In the supine posture obese patients can generate significant levels of iPEEP that contribute to increased levels of neural respiratory drive compared with the upright posture. There has been much debate regarding the optimal ventilator strategy in patients with obesity related respiratory failure, with uncontrolled trial data to support simple continuous positive airway pressure, pressure support (PSV) NIV and volume targeted (VT) NIV. There has been no robust evidence to suggest superiority of a single mode but post hoc data suggests superior control of sleep disordered breathing in patients in pressure controlled mode. It is unclear whether the extended inspiratory time of pressure controlled mode is allowing superior gas exchange by maintaining airway distension and preventing regional collapse.